Fluid pressure producing device



oct.' 13, 1942. H c. swn-T 2,298,848

*l FLUID 'PRESSURE PODUCING DEVICE Filed Oct. 5, 1940 /22 faz Y i I IVENTOR. EL@ E B15/@evry C `SLV/Fr ATTORNEY.

Patented Oct. 13, 1942 UNITED STATES l This, invention relates to fluid pressure pronzasaars y FLUm'raEssUaa PaonUciNG nevica f nai-vc c. swift, ncacit, Mich., csacncr'fc ny- 'draulic Brake Company, Detroit', Mich., a corporation f California Application octcbcr 5, 19110, scrici Nc. 359,965 'z claims. kol. so-54.6)

ducing systems. and more particularly to uidy the chamber'52 and the small chamber 26.

' trusion 50 to provide ,a communication.. between pressure producing devices for such systems. ,y

An object of the invention is to provide a fluid .pressure producing device of the two-phase type a iiuid pressure producing device operative tot 1o eflect a gradual transition from lowto high pressure without proportionately increasing the applied or actuating force.

Otherobjects and advantages .of theinvention will appear from the following description taken 15 in connection with the drawing forming a part ofthis specification, and in which,

IFig. 1 is a schematic viewV of a fluid pressure braking system `embodying the invention;

Fig. v2 isa sectional view of a fluid pressure 20 producing device vincorporated in the system.; and Fig. 3 is a sectional view taken on line 8-8 c -of Fig. 2.

Referring to the drawing for, more speciiic details of the-invention, i6 represents a duid pres- .25 sure producing device including a reservoir I2 having a removable top I4 provided with a illling opening i6 normally closed as by a plug I8 ,having openings therethrough for venting the reservoir to the atmosphere.

A cylinder 22 depending from the bottom of the reservoir includes a .large chamber 24 opening into the reservoir and a relatively small chamber v26 arranged below, concentrically to, and in direct communication with a largel chamber and providing at its'juncture therewith an annular. shoulder 28, and the smallchamber 26 is closed by. a head 2U provided with a discharge port 82 controlled as by a two-way valve `84.

. A piston 36 reciprocable in the chamber 24 is 40 held.' against rdisplacement by a1 retaining ring 88 seated in, a groove in the wall of the chamber adjacent its open end. The piston includes a head 40 and a skirt 42 providing a chamber 44 back of' the head, and arranged concentrically on 45 `.the head is an extension .48 projected through the chamber 24 and into the chamber 28, and

` provided on its head 48 with a cylindrical protrusion 80. The'extension is bored to provide a chamber 82 openinginto the chamber 44 back 50' of the head o! the piston. Arranged in thewall -of the chamber 82 isa port I4 providing a communicaltion between the chamber l2 'and theV large chamber 24. .The chamber 624 also has a A sealing cup 58 sleeved over the extension 46 and sealed on the head of the piston 36Ainhibits seepage of fluid from the chamber 24 past the piston, and a. spring 68 interposedV between the cup 58 and a washer 62 seated on the annular shoulder 28 serves to` retain the cup against displacement and also to return the'piston to its retracted position.

A piston 64 reciprocablein the small chamber 26 normally seats on the washer 62. The piston 64'includes a head 66 and a skirt 68 providing a chamber 10 back of the head. I The chamber 1D opens into the chamber 24, and a concentric opening l2 through the headv of the piston provides a communication between the chambery 10 and the small chamber 2 6. Theopening. 12 -receives the protrusin on the head of the extension' upon movement of the piston 36 toclose the communication between the chamber 26and the chamber 10.

A sealing cup 14 seated on .the headof ,the piston 64 seals the piston in the vchambe 6. 'I'he cup has a concentric opening 16, an.

perimeter defining this opening 16 overhangs the opening" Ill in the head of the piston soas to abut and seal the protrusion 50 in the opening 10,

. and a spring 16 interposed between the cup 14 and the two-wayvalve 34 serves to retainA the cup and valve against displacement and also to return the piston 62 to its' retracted position against the stop 62.'

\ A plunger reciprocabl/e in the chamber 52 has on one end a head 82 supporting a .sealing cup 84. The other end of the'plunger has a reduced portion providing an annular passage 86 communicating with the port 54, also with the chamber 44 and a valve head 88 in the chamber 44 forv control of the passage 86 having an upstanding oset flange 80. A pressure block B2 4slidable in the chamber 44 is held against displacement by a retaining ring 94 seated in a groove in the wall of the chamber. The block 82 ilange. 96, and a plurality of spaced passages `$18 therethrougnproviding communications between the chamber 44 and a reservoir. .The flange 96 normally seats on a retaining' ring Hill iitted-in a groove in the wall-of the sleeve 86. A spring |02 interposed between the valve 88 and the block 92 urges the flange 80 on the valve head 68 to its seat, and a spring |84 interposed between the bottom of the chamber 44 and the block 82 urges portttextended'through the head 44 and pro- 56 theblockl to itssretracted yposition against the y retaining ring 94 so as to normally maintain valve 88 open.

A rotatable shaft |06 mounted transversely of the reservoir has thereon an actuator |08 engag. ing the pressure block 92, and a crank connested by a rod ||2' toa foot pedallever ||4 rockable on a stub shaft ||6 and connected by a retractile spring ||8 to a fixed support |20.

Fluid pressure delivery pipes or conduits |22 and` |24 connected to the discharge port 32 have branches connected respectively to fluid pressure actuated motors |26, preferably arranged inL pairs, one pair for actuating brakes associated with the front wheels of a vehicle, and another pair for actuating brakes associated withthe rear wheels of a vehicle.

The brakes may be of any preferred structure. As shown, each of the brakes includes a fixed support or backing plate |28, a rotatable drum |30 associated therewith, a pair of friction elements the or shoes |32 pivoted on the backing plate for cooperation with the drum, a retractile spring |84 connecting the shoes, and a motor mounted on the backing plate and connected to the shoes for actuating` the shoes into engagement with the drum against the resistance of the retractile spring.

In a normal operation, upon depressing lthe foot pedal lever ||4, force is transmitted therefrom through the rod I2, the crank ||0, the shaft |06 and the actuator |06 to the pressure block 92, resulting in movement of the block against the resistance of, the spring |04. This movement of the block results in closing the valve 88, slight compression of the spring |02 to imposela predetermined load on the valve, and thereafter the pressure block 92 4and the piston 36 move as a unit.

pressure delivery lines |22 and |24 and the branches thereof into the fluid pressure actuated motors |26, causing energization of the motors and resultant actuation of the friction elements |32 into engagement with the drums |30 against the resistance of the retractile springs |34 .effectively retarding rotation of the drums. Inasmuch as initial movement of the block 82 results in closing of valve 88, chamber 24 is closed to communication with the reservoir, with consequent necessity for displacement of fiuid from the chamber as the piston 36 is advanced.' As the. piston-ls thus advanced and pressure is developed within the chamber, a velocity head is established, permitting a flow of fluid through the chamber 10 and port 12 into the braking system. The fluid under pressure thus displaced from chamber 24 moves piston 64 relative to moving extension 48--50 so as to provide a passage for the fiow of fluid through 10-12. I

Upon attaining a predetermined pressure on lthe fluid in the chambers 24 and 26, the pressure 64 on the compression stroke, the fluid in the chamber 26 is displaced therefrom. past the twoway valve 34, through the discharge port and the duid pressure delivery lines into the motors, causing further energization of the motors to increase the activating force of the friction elements without'proportionately increasing the ap- I plied or operating force.

Upon conclusion of a braking operation, the foot pedal lever I4 is released, and returns to its retracted position under the influence of the retractile spring H8. As the foot pedal lever returns to its retracted position, the rod'||2 is retracted, and this movement of the rod transmits force to the cranky |I0, causing slight rotation of the shaft |06, resulting in retraction of the actuator |08 and release of the pressure block 32.

Upon release of the applied force, the pistons 36 and 64 are returned to their respective retracted positions under the iniiuence of the retractile springs 60 and 18. As the pistons move to their retracted positions, there is relative movement between the pistons, resulting in opening the port 12 and establishing communication between the chambers 24 and 26. Also there isl relative movementbetween the piston 36 and the pressure block 82. resulting in opening theA valve 88 and consequent establishment of communication between the chamber 24 and the reservoir.

During this operation, a partial vacuum. is

-created in the chamber 26, and this results in turned to the reservoir.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

I claim:

1. A fluid pressure producing device comprising a cylinder vhaving a large chamber and a relatively small chamber, a piston reciprocable in the cylinder having a large piston and a small piston complementary to the chambers, a valve in each of the pistons normally open, the valve in the large piston operative to close upon initial movement of the piston, 4the valve in the large piston lishes communication between the chamber 24 and the reservoir by way of the port 54, the pas- V sages 86, the chamber 44 in the piston 34, and the Upon further movement of the pistons 36 and 75 operative to open upon attaining a predetermined pressure in the chambers, and the valve in the of the valve in the large piston.

2. A liuid pressure producing device comprisinga cylinder having a large chamber and a relatively small chamber, a piston reciprocable in the cylinder havinga large head and a small head complementary to the chambers, a valve in each of the heads normally open, an actuator for the piston operative to close the valve in the large head upon initial movement ofI the piston, the valve in the large head operative to open as a result of` the combined attained predetermined pressure in the chambers resisted by the'activating force on the piston. and the valve in the small chamber operative to close concomitantly with the opening of the valve in the large chamber.

- communicating therewith,

3. A fluid pressure producing device comprising a cylinder having a large chamber and a relativeclosing the opening at precisely the time the valve opens.

4. A fluidpressure producing device comprising a'reservoir, a cylinder depending therefrom and including' a chamber and a relatively small chamber below the large chamber, a piston reciprocable in the cylinder having a large head and a small head complementaryto the chambers, a valve in each of the heads open when the piston is at rest, the valve in the large head operative to close upon initial movement of the piston, the valve in the large head operative to open upon attaining a predetermined-pressure'win the chambers followed by the closing of thevalve in the small head as a result of diilerentialin pressure in the chambers present after the valve opens in the large head.

5. A fluid 'pressureproducing device comprising, a cylinder having a large chamber and a relatively small chamber, a piston reciprocable therein having 4heads complementary to the chambers, means for actuating the piston, a valve in each head normally open, and means associated with the piston actuating means for closing the valve m the large Bead upon initial 'actuation or the piston, said valve operative to open upon attainlarge ing a predetermined pressure in the chambers as the piston is further advanced.

v 6. A huid pressure producing device comprising a reservoir, a cylinder `associated therewith having a large chamber and a relatively small chamber, a piston reciprocable in the cylinder having a large head and a small head complementary to the chamber, a valve in the large head normally open to provide communication between' the reservoir andlarge chamber, a `valve in the smallhead providing communication between the large and smallv chambers, an actuator for the piston, and resilient means cooperating with the actuator for closing the'valve in the large head upon initial movement of the piston, said valve responsive to open against the resistance of the resilient means upon attainment of a predetermined pressure on the fluid in the chambers as the piston is further advanced Ato provide communication between th'e large chamber and reservoir.

7. A iluid pressure producing device comprising areservoir. a cylinder associated therewith having a large chamber and a small chamber, a

pistonv reciprocable in the cylinder having a large head and a small head complementary to the chambers,4 an actuator for the piston, a chamber in the large head of the piston, passages in the large head providing communication between the large chamber and reservoir. a piston reciproca-v ble in the piston chamber having passages therethrough, a valve intermediate the passages in the large head and the piston reciprocable in the piston chamber normallyl open, a vspring inter- 

